Ultra high-sensitivity micro magnetic sensor

Abstract

A magnetic sensor, comprising: a substrate having a groove; two conductive magnetic wires for magnetic field detection arranged adjacent and substantially parallel to one another and at least partially recessed in the groove on the substrate, the two conductive magnetic wires electrically coupled at one end; a coil surrounding the two magnetic wires; two electrodes coupled to the two conductive magnetic wires for wire energization; and two electrodes coupled to the coil for coil voltage detection.

The invention claimed is: 
     
       1. A magnetic sensor, comprising:
 a substrate having a groove; 
 two conductive magnetic wires for magnetic field detection arranged adjacent and substantially parallel to one another and at least partially recessed in the groove on the substrate, the two conductive magnetic wires electrically coupled at one end; 
 a coil including a lower part and a upper part and surrounding the two magnetic wires; 
 two electrodes coupled to the two conductive magnetic wires for wire energization; and 
 two electrodes coupled to the coil for coil voltage detection, wherein 
 the two conductive magnetic wires have a two-phase magnetic domain structure of a surface magnetic domain with circumferential spin alignment and center core magnetic domain with longitudinal spin alignment, 
 the two conductive magnetic wires are arranged over the lower part of the coil, and are fixed and covered by an insulating resin, and 
 the upper part of the coil is provided on the insulating resin. 
 
     
     
       2. The magnetic sensor of  claim 1 , wherein the two conductive magnetic wires are formed of a CoFeSiB amorphous alloy with a diameter in the range of about 5 μm to about 20 μm and the length of each of the two conductive magnetic wires is in the range from about 0.07 mm to about 1.0 mm. 
     
     
       3. The magnetic sensor of  claim 1 , wherein the two conductive magnetic wires have a magnetic anisotropy field of 20 G or less. 
     
     
       4. The magnetic sensor of  claim 1 , wherein the coil as a coil pitch of 10 μm or less. 
     
     
       5. The magnetic sensor of  claim 1 , wherein the number of windings of the coil is in the range from about 6 to about 180. 
     
     
       6. The magnetic sensor of  claim 1 , wherein the space between the coil and the two conductive magnetic wires is about 3 μm or less. 
     
     
       7. The magnetic sensor of  claim 1 , wherein the upper part of the coil is provided on the insulating resin using photolithography. 
     
     
       8. The magnetic sensor of  claim 1 , further comprising:
 a pulse current applying circuit configured to apply a pulse current to the magnetic wires; 
 a coil voltage detecting circuit configured to detect a coil voltage occurred when the pulse current is applied to the two magnetic wires; and 
 a voltage converting circuit configured to convert the coil voltage into an external magnetic field H. 
 
     
     
       9. The magnetic sensor of  claim 8 , wherein
 the pulse current applied to the magnetic wires has a pulse frequency of 0.2 GHz to 4.0 GHz, and has a strength required to generate over a 1.5 times larger circumferential magnetic field than the anisotropy field on a surface of the wire. 
 
     
     
       10. The magnetic sensor of  claim 8 , wherein
 the voltage converting circuit is configured to convert the coil voltage into the external magnetic field H using an equation:
     Vs=Vo· 2 L·πD·p·Nc·f ·sin(π H/ 2 Hm ),
 
 
 where Vs is a coil output voltage and Vo is a constant of proportionality, and as a control factor constant, L is a wire length, D is a wire diameter, is a skin depth of a pulse current, Nc is number of winding of a coil, f is a pulse frequency, and Hm is an external magnetic strength to obtain a maximum coil output voltage. 
 
     
     
       11. The magnetic sensor of  claim 8 , wherein
 the pulse current applying circuit comprises a pulse generating circuit configured to generate the pulse current, and 
 the coil voltage detecting circuit comprises an input circuit, a pulse compliant buffer circuit configured to input the coil voltage, a sample hold circuit with an electronic switch configured to detect a peak voltage of an output waveform of the coil voltage, a capacitor with a capacitance of 4 to 100 pF configured to hold the peak voltage, and an programming amplifier configured to perform amplification before AD conversion. 
 
     
     
       12. A magnetic sensor, comprising:
 a magnetic field detection element including two conductive magnetic wires for magnetic field detection arranged adjacent to one another on a substrate, a coil including a lower part and a upper part and surrounding the two conductive magnetic wires, two electrodes coupled to the two conductive magnetic wires for wire energization, and two electrodes coupled to the coil for coil voltage detection; 
 first circuitry electrically coupled to the two electrodes for energization of the two conductive magnetic wires configured to apply a pulse current to the two conductive magnetic wires in opposite directions; 
 second circuitry electrically coupled to the two electrodes for coil voltage detection configured to detect a coil voltage when the pulse current is applied to the two magnetic wires; and 
 third circuitry electrically coupled to the second circuitry configured to convert the coil voltage into a voltage representing the magnitude of an external magnetic field H, wherein 
 the two conductive magnetic wires have a two-phase magnetic domain structure of a surface magnetic domain with circumferential spin alignment and a center core magnetic domain with longitudinal spin alignment, 
 the two conductive magnetic wires are arranged over the lower part of the coil, and are fixed and covered by an insulating resin, and 
 the upper part of the coil is provided on the insulating resin. 
 
     
     
       13. The magnetic sensor of  claim 12 , wherein the two conductive magnetic wires have a magnetic anisotropy field of 20 G or less. 
     
     
       14. The magnetic sensor of  claim 12 , wherein the pulse current applied to the two conductive magnetic wires has a pulse frequency in the range of 0.2 GHz to 4.0 GHz. 
     
     
       15. The magnetic sensor of  claim 12 , wherein the pulse current applied to the two conductive magnetic wires has the strength required to generate over a 1.5 times larger circumferential magnetic field than the anisotropy field on a surface of the two conductive magnetic wires. 
     
     
       16. The magnetic sensor of  claim 12 , wherein the coil has a coil pitch of 10 μm or less. 
     
     
       17. The magnetic sensor of  claim 12 , wherein the third circuitry is further configured to:
 detect a peak of the coil voltage, 
 hold the peak voltage, and 
 amplify the held peak voltage. 
 
     
     
       18. The magnetic sensor of  claim 12 , wherein the upper part of the coil is provided on the insulating resin using photolithography.